In biomedical applications, optical detection techniques are often relied on to measure micro samples, such as absorption states of red blood cells etc., to a particular light, in order to respond the content or the composition ratio of specific substances within the cells. Generally speaking, the conventional optical detection techniques usually use laser light as a light source. However, the size and power consumption of the laser light source is large, and its price is relatively high, which makes the optical measuring apparatus expensive. In contrast, light emitting diodes (LEDs) are relatively small, cheap, low power consumption, and low heat generation, as the semiconductor technology has been progressively developed in recent years. As a result, the light emitting diodes have gradually replaced the laser light source to be the light source for certain biomedical detection apparatus.
However, the light shape and intensity distribution of a common light emitting diode are not uniform, which could cause difficulties in optical alignment for the measurement within a micro-volume sample. This may significantly affect the accuracy and resolution of the optical detection, and thus limit the application of light emitting diodes optical detection for biomedical applications. In some cases, when a plurality of light emitting diodes are used in an optical measurement apparatus, a plurality of light beams emitted from the light emitting diodes may generate light-signal interferences between each other. Such interference normally increases the measurement noise, causes skewed optical signal, and may result in misjudgment of the sample conditions. Thus apparatus and methods to overcome such limitations of LEDs in biomedical measurement devices are needed.